This invention relates generally to a structure for combining the outputs of plural two-terminal radio frequency generating devices. More particularly, this invention relates to a structure for combining the outputs of electron-bombarded semiconductor radio frequency generating devices. More particularly, this invention relates to a structure for combining the outputs of electronbombarded semiconductor radio frequency devices coupled to a load.
Although circuits for combining the outputs of electron-bombarded semiconductor diodes are known in the art they suffer a number of disadvantages. When diodes are paralleled the impedance of output coupling components becomes excessively low as the outputs of an increasing number of diodes are paralleled particularly at higher frequencies. As a result, excessive power losses occur due to fixed stray resistances in the output circuit and the large output coupling transformer ratios which are required to couple to conventional loads. Physically combining plural diodes into one diode having a combined area is not advantageous because the electrical equivalent circuit of the combined area diode remains the same as plural paralleled diodes.
Hybrid combining circuits such as a "Magic-T" or Balun maintain impedance levels when diodes are combined but they have other serious disadvantages. Particularly in broadband operation, the harmonics in the generated signal are loaded by the output circuit thus decreasing the maximum power limitation permissible for a given radio frequency (RF) voltage swing. Further major disadvantages of hybrid circuits are excessive complexity, cost and fabrication difficulty. Thus there is a need for a circuit for combining the outputs of plural EBS diodes in a single EBS source for coupling energy to a load.